Interfacial reactions between different Sn-based lead- free solder alloys and CuNi substrates

The effect of the presence of Ni in Cu substrates on the interface reaction during soldering and the growth of Sn-Cu intermetallic compounds (IMCs) was studied. The study involved reflow soldering of Sn-0.7Cu, Sn- 3Ag-0.5Cu and Sn-0.7Cu-0.05Ni lead-free solders on pure Cu and Cu-6Ni substrates with holding times of 5, 10 and 15 minutes at 232 °C. The presence of 6 wt% Ni in the Cu substrate strongly affects the microstructural evolution and the growth of the IMCs. The presence of Ni in the substrate significantly increased the overall thickness of the (Cu,Ni)₆Sn₅ layer while suppressing the formation of the Cu₃Sn layer. The thickness of the (Cu,Ni)₆Sn₅ layer increased with reflow time for both Cu and Cu-6Ni substrate. (paper)